Sensor apparatus for monitoring at least one battery cell

ABSTRACT

A sensor apparatus (10) for monitoring at least one battery cell (20) of a battery system (100), having a sensor element (11) for detecting at least one state variable of the battery cell (20), at least one electrically and/or thermally conductive connecting element (12) connected to the sensor element (11) so that the sensor element can be connected to the battery cell (20) and to an electronic unit (30) of the battery system (100), wherein the connecting element (12) is formed as a flexible printed circuit board (12).

BACKGROUND OF THE INVENTION

The present invention relates to a sensor apparatus and to a batterysystem.

Temperature sensors are known from the prior art, wherein the sensorapparatuses have a sensor element comprising connection lines, each ofwhich is secured to a corresponding electrode on a temperature detectionelement. DE 100 15 831 A1 shows a sensor apparatus of this kind.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a sensor apparatus formonitoring at least one battery cell of a battery system is claimed. Thesensor apparatus has a sensor element for detecting at least one(physical and/or chemical) state variable of the battery cell and atleast one electrically and/or thermally conductive connecting elementconnected to the sensor element so that the sensor element can beconnected to the battery cell and to an electronic unit of the batterysystem. The connecting element is formed as a flexible printed circuitboard; in particular, the flexible printed circuit board is formed, atleast longitudinally, in an elastic manner. In the context of theinvention, a flexible printed circuit board can be a cable formed with aplurality of cores (FFC) comprising a plurality of lines or a printedcircuit on a flexible plastics carrier (FPC). The plastics carrier canpreferably comprise polyimide, Mylar, nylon and/or polyester film.Copper or silver is conceivable as conductor material; the contactregions can also be flash plated for enhanced demands. In particular,the lines can be arranged alongside one another in a parallel andelectrically insulated manner and can be formed as signal lines. Aflexible printed circuit board according to the invention can compensatefor tolerances or movements related to components or induced bymechanical influences. Generic sensor apparatuses are installed inbattery systems. The electrically and/or thermally conductive connectingelement is connected at a first end thereof to an electronic unit, forexample in the form of a PCB board. PCB boards of this kind have certainproduction-related tolerances and are generally mounted on structuralcomponents, for example a cover of a battery system. The installationposition of the battery systems is consequently afflicted by tolerances,wherein the spacing between the electronic unit and the battery cell canvary accordingly. A sensor apparatus according to the invention cancompensate for such tolerances by virtue of the connecting element beingformed as a flexible printed circuit board. In particular, the flexibleprinted circuit board is formed, in terms of its length and thuslongitudinally, in an elastic and/or flexible manner. An electronic unitof a battery system can in this case be, for example, a batterymanagement system (BMS) and/or a cell supervision circuit (CSC). Theflexible printed circuit board according to the invention is connectedin this case at another end to a sensor element so that the sensorelement is pressed onto the battery cell, in particular onto theterminal of a battery cell, on account of the flexible configuration.The flexible printed circuit board is preferably formed in such a waythat a spring force can be generated by the geometric shape of theprinted circuit board so that the sensor element can be brought intocontact with the battery cell. The sensor element of the sensorapparatus according to the invention can be formed, for example, as atemperature sensor so that the invention can also involve a temperaturesensor apparatus. In this case, the sensor element can be formed as anelectrical or electronic component, in particular a semiconductorcomponent, so that an electrical signal as a measure for thetemperature, for example, can be transmitted to an electronic unit. Itis conceivable for the sensor element (for example the semiconductortemperature sensor) to be integrated in the connecting element or to bearranged thereon in a force-fitting and/or form-fitting manner at leastin sections. Furthermore, the sensor element can be signal-connected toa sensor unit arranged on the battery cell, preferably on the terminalof a battery cell. In the context of the invention, the sensor elementcan be formed as a passive or an active component. The sensor elementcan be formed as a hot conductor, cold conductor or semiconductortemperature sensor element. It is likewise conceivable for the sensorelement to be formed as a thermocouple, a ferromagnetic temperaturesensor element or as a fiber-optic temperature sensor. The flexibleprinted circuit board is preferably formed with a plurality of cores; inparticular, it can be formed in a material-bonded manner, for examplesoldered or welded, to the sensor element. The sensor element canpreferably be formed in a manner integrated in the flexible printedcircuit board, in particular in one piece with the flexible printedcircuit board.

Further features and details of the invention emerge from the dependentclaims, the description and the drawings. In this case, it goes withoutsaying that features and details, which have been described inconnection with the apparatus according to the invention, naturally alsoapply in connection with the system according to the invention and/orthe method according to the invention and vice versa in each case, withthe result that reference is or can be always reciprocally made withrespect to the disclosure relating to the individual aspects of theinvention.

The flexible printed circuit board can advantageously have at least onespring element, wherein, in particular, the spring element and theflexible printed circuit board are formed in one piece. The springelement can press the sensor element against the battery cell, inparticular a terminal of the battery cell. The contact between thesensor element and the battery cell can thus be ensured in spite ofproduction-related and/or movement-related tolerances. In this case, thespring element makes it possible to achieve tolerance compensation in atleast the longitudinal direction of the connecting element. The springelement can comprise a plastic and/or metal. It is further conceivablefor the spring element to be formed by the flexible printed circuitboard. For this, the flexible printed circuit board can be shaped and/orreshaped in such a way that the connecting element can be elasticallydeformed. The flexible printed circuit board can thus store potentialenergy. The spring element can provide a constant restoring force sothat the sensor element is pressed onto the battery cell, in particularonto the terminal of the battery cell. The spring element can comprise asteel, in particular spring steel and/or copper alloys, in particularcan be formed as a semi-finished product, for example as a narrow stripand/or wire. Furthermore, it is conceivable for the spring element tocomprise rubber or plastic.

The spring element and the flexible printed circuit board canadvantageously be formed at least in a force-fitting, material-bondedand/or form-fitting manner. This can achieve a compact physical shape,wherein the flexible printed circuit board and the spring element aresimultaneously formed in a mechanically stable and flexible manner withrespect to one another. A force fit can be produced, for example, bydrilling or additional securing means. The spring element and theflexible printed circuit board can be connected to one another in amaterial-bonded and/or form-fitting manner by injection-molding and/oradhesive bonding and/or welding.

It is conceivable for the flexible printed circuit board and/or thespring element to be of helical, spiral or z-shaped form. The shape ofthe spring element makes it possible for it to be formed in a compactmanner in the relaxed state and for it to compensate for tolerances, inparticular in the longitudinal direction, in the event of having atensile force or a pressure force applied to it and thus in the event ofthe connecting element pulling apart or being compressed.

It is furthermore advantageous when an insulation element is provided sothat the flexible printed circuit board is at least electricallyisolated, in particular with respect to the spring element. Theinsulation element preferably serves as protection against a shortcircuit of the flexible printed circuit board with a further componentof the battery cell or of the battery system. It is further conceivablefor the insulation element to be able to reduce interference influences,in particular electrical or electromagnetic interference influences. Theinsulation element can in this case be formed at least in sections,preferably over the entire length of the printed circuit board. It isconceivable for the insulation element to comprise a plastic and, inparticular, to be arranged in a form-fitting manner on the springelement and/or on the flexible printed circuit board. It can bepreferred when the insulation element is formed in a film-like manner,in particular, comprising a thermoplastic. The insulation element canencase the individual cores of the flexible printed circuit board atleast in sections. The insulation element preferably has a materialrecess at the ends of the flexible printed circuit board at which thesensor element or the electronic unit is arranged.

There can also be provision for the spring element to at least partly orelse completely comprise foam as material, wherein, in particular, thefoam is elastic. Deformation of the foam in this case generates arestoring force, which is used as spring force. It can thus beadvantageous when at least one spring element is of foamed form. Thespring element that is of foamed form can preferably be of rectangular,cylindrical or trapezoidal form. In particular, the foamed springelement can comprise a plastic, preferably EPDM. It is conceivable forthe foamed spring element to be adhesively bonded, welded, latched orclipped to the flexible printed circuit board. Corresponding latchingand/or clip elements can be present for this purpose. A spring elementof foamed form can be arranged in a thermally, magnetically and/orelectrically insulating manner between the battery cell and theelectronic unit. Furthermore, a spring element of foamed form cancompensate for component or movement tolerances. It is conceivable forthe spring element of foamed form to have a recess for the sensorelement. It is also conceivable for the spring element to be injectedonto the printed circuit board of flexible form. The foamed springelement can preferably have a height, a cross section and/or a diameterbetween approximately 1 mm and approximately 30 mm, preferably betweenapproximately 5 mm and approximately 15 mm. It can be advantageous whenan insulation film is arranged on the sensor element, as a result ofwhich the sensor element is electrically and/or thermally insulated atleast in sections. The insulation film ensures that no voltage can betransmitted from the battery cell, for example, via the spring element.Furthermore, an insulation film can thermally insulate the springelement and the sensor element from one another so that no interferenceinfluences for the electronic unit and/or for the sensor element cannegatively influence a measurement result. Consequently, it is possiblefor a state variable of the battery cell to be measured precisely and ina manner substantially free from interference influences. The insulationfilm can in this case be formed from a single material, in particular ina material-bonded manner or in one piece with the insulation element.The insulation film is advantageously formed by the insulation element.

It is conceivable for the connecting element to have a plug at least atits one end. The plug is preferably arranged at the end of theconnecting element, which is signal-connected to the electronic unit.Consequently, the plug is formed on the connecting element preferably insuch a way that it can be plugged onto the electronic unit before theelectronic unit is mounted in the battery system. The connecting elementcan thus be connected to the electronic unit in a force-fitting and/orform-fitting manner. After the installation of the electronic unit inthe battery system, the flexible printed circuit board can be broughtinto contact with the battery cell, in particular the terminal of thebattery cell, on account of the spring force. In this case, the plug ispreferably a pin-type plug connector, a soldering adapter or plugconnector, in particular having a mounting aid. The plug makes itpossible to mount the sensor apparatus on the battery system in a simpleand cost-effective manner. The mounting aid can in this case be formedas a tool receptacle, as a result of which the mounting or theconnection of the plug to the electronic unit can be improved.

The spring element and/or the flexible printed circuit board canadvantageously have at least one latching connection, clip connection orclamping connection, as a result of which the spring element and theflexible printed circuit board can be connected in a force-fittingmanner. In this case, the latching connection, clip connection orclamping connection can be formed on the spring element and/or on theflexible printed circuit board. The spring element can advantageouslyhave such a connection at least in sections. In this case, it isconceivable for the spring element to be formed as a stamped part and tohave lugs at least in sections, which can be bent around the flexibleprinted circuit board after the flexible printed circuit board has beenmounted on the spring element.

It is preferred when the insulation element and/or the insulation filmcomprise at least plastic and/or ceramic. A plastic makes electricaland/or thermal insulation possible and is cost-effective and simple toproduce. A ceramic has good thermal and electrical insulation; inparticular, a ceramic is not sensitive to higher temperatures. Inparticular, an insulation element and/or an insulation film, comprisinga ceramic, on the sensor element can be advantageous since influencescaused by temperatures, in particular high temperatures, can besubstantially prevented.

According to a second aspect of the invention, a battery system forstoring electrical energy and for supplying electrical energy to anelectric motor of a motor vehicle is claimed. The battery system has atleast one battery cell, an electronic unit for monitoring the batterysystem and at least one sensor apparatus for monitoring at least onebattery cell. Here, the sensor apparatus has a sensor element fordetecting a state variable of the battery cell, at least oneelectrically and/or thermally conductive connecting element forconnecting the sensor element to an electronic unit of the batterysystem, wherein the connecting element is formed as a flexible printedcircuit board.

The sensor apparatus of the battery system is advantageously formedaccording to the invention. All of the advantages that have already beendescribed in connection with the sensor apparatus according to theinvention thus result for the battery system.

Further measures that improve the invention result from the followingdescription of some exemplary embodiments of the invention, which areschematically illustrated in the figures. All of the features and/oradvantages, including structural details and spatial arrangements,emerging from the claims, the description or the drawings can beessential to the invention both on their own and also in an extremelywide variety of combinations. It should be noted here that the figuresare merely descriptive and are not intended to limit the invention inany way.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following figures, identical reference symbols are used for thesame technical features, even of different exemplary embodiments. In thefigures:

FIG. 1 shows a first embodiment of a battery system according to theinvention comprising a sensor apparatus according to the invention,

FIG. 2 shows one possible embodiment of a sensor apparatus according tothe invention,

FIG. 3 shows a further possible embodiment of a sensor apparatusaccording to the invention,

FIG. 4a shows one possible embodiment of a battery system according tothe invention,

FIG. 4b shows a further possible embodiment of a battery systemaccording to the invention, and

FIG. 5 shows a further possible embodiment of a sensor apparatusaccording to the invention.

DETAILED DESCRIPTION

FIG. 1 shows a first possible embodiment of the battery system 100according to the invention for storing electrical energy and forsupplying electrical energy to an electric motor of a motor vehicle. Thebattery system 100 has at least one battery cell 20, an electronic unit30 for monitoring the battery system 100 and a sensor apparatus 10 formonitoring the at least one battery cell 20. The sensor apparatus 10according to the invention has a sensor element 11 for detecting a statevariable of the battery cell 20, wherein at least one electricallyand/or thermally conductive connecting element 12 connects the sensorelement 11 to an electronic unit 30 of the battery system 100 andwherein the connecting element 12 is formed as a flexible printedcircuit board 12. In FIG. 1, the electronic unit 30 is formed as aprinted circuit board (PCB) and is arranged on a cover 110 of thebattery system 100. The electronic unit 30 is signal-connected to thebattery cell 20 by means of the connecting element 12, wherein theconnecting element 12 is formed as a substantially z-shaped flexibleprinted circuit board. The flexible printed circuit board 12 formed in asubstantially z-shaped manner forms spring elements 13 at the kinks ofthe flexible printed circuit board 12, with the result that, on the onehand, the z-shaped geometry of the flexible printed circuit board 12and, at the same time, spring properties are formed. Consequently, thesensor element 11 is pressed onto the battery cell 20, in particular theterminal of the battery cell 20. At the other end of the flexibleprinted circuit board 12, said end is connected to the electronic unit30 in a force-fitting and/or form-fitting manner so that the resultingspring force can support the flexible printed circuit board 12 on theelectronic unit 30 and is pressed in the direction of the battery cell20. In FIG. 1, the sensor element 11 is arranged on the flexible printedcircuit board 12 and is formed in one piece therewith. In this case, thesensor element 11 can be integrated in the flexible printed circuitboard 12. The flexible printed circuit board 12 is preferably formedwith a plurality of cores and is encased by an insulation element 14, inparticular a film-like insulation element 14.

FIG. 2 shows a further embodiment of a sensor apparatus 10 according tothe invention. In FIG. 2, the sensor apparatus 10 has a connectingelement 12, which, as a flexible printed circuit board 12, is formed ina substantially z-shaped manner. The flexible printed circuit board 12is furthermore formed with a plurality of cores and has a sensor element11 at its first end and a plug 16 at its second end 17, wherein the plug16 is arranged on the electronic unit 30 in a plug receptacle in aforce-fitting and/or form-fitting manner. In FIG. 2, the plug 16 of thesensor apparatus 10 has a tool receptacle 16.1, wherein the toolreceptacle simplifies mounting of the sensor apparatus 10 on theelectronic unit 30. It is thus possible, when mounting the sensorapparatus 10 on the electronic unit 30, to fix a tool, for example apair of pliers, to the tool receptacle 16.1, which is formed in FIG. 2as two laterally arranged lugs, as a result of which simplified pluggingof the plug 16 into a plug receptacle of the electronic unit 30 is madepossible. The substantially z-shaped flexible printed circuit board 12formed with a plurality of cores has a sensor element 11 at its firstend, which sensor element is formed in one piece with the flexibleprinted circuit board 12. The sensor element 11 likewise has a toolreceptacle 11.1, wherein the tool receptacle 11.1 of the sensor element11 likewise simplifies mounting of the sensor element 11 on the batterycell 20, in particular a terminal of the battery cell 20. The toolreceptacles 11.1 of the sensor element 11 are in this case shaped asbores of the sensor element 11 formed in a substantially planar manner.A second tool receptacle 11.1 is in this case formed in the sensorelement 11 in a linear manner, for example in a slot-shaped manner, andlikewise makes simplified mounting of the sensor element and thus thesensor apparatus 10 on a battery cell 20 possible. The plug 16 on thesecond end 17 of the flexible printed circuit board 12 and the sensorelement 11 are formed in one piece with the flexible printed circuitboard 12. In this case, it is conceivable for the sensor element 11 tobe welded or soldered or crimped to the flexible printed circuit board12 formed with a plurality of cores. In FIG. 2, the plug 16 is formed asa flat plug and can preferably be plugged into the electronic unit 30first when the sensor apparatus 10 is mounted. The electronic unit 30 ispreferably arranged in a cover of the battery system, for example hookedin or screwed thereto, so that, when the cover of the battery system ismounted, the sensor element 11 is pressed onto the battery cell 20 onaccount of the flexible printed circuit board formed in a z-shapedmanner. The spring elements 13 form at the kinks of the flexible printedcircuit board 12 on account of the z-shaped configuration of theconnecting element 12.

FIG. 3 shows a three-dimensional view of a further embodiment of asensor apparatus 10 according to the invention. In this case, the sensorapparatus 10 has, on its second end 17, a plug 16, a connecting element12 in the form of a flexible printed circuit board 12 formed with aplurality of cores (a plurality of lines is meant) as well as a sensorelement 11, wherein the individual lines (e.g. 6 lines here) can beclearly recognized alongside one another. In FIG. 3, the flexibleprinted circuit board 12 is formed with a plurality of cores and in asubstantially z-shaped manner, wherein spring elements 13 form at thekinks of the flexible printed circuit board 12. In FIG. 3, the sensorelement 11 has an insulation film 15 so that the sensor element 11 iselectrically and/or thermally insulated. The sensor element 11 iselectrically connected to the flexible printed circuit board 12 so thatstate variables of a battery cell 20 can be transmitted from the sensorelement 11 via the connecting element 12 formed as a flexible printedcircuit board 12 to an electronic unit 30. In FIG. 3, the flexibleprinted circuit board 12 has an insulation element 14 so that theflexible printed circuit board 12 is at least electrically and/orthermally insulated. The insulation element 14 is preferably formed in afilm-like manner and in a form-fitting manner with the flexible printedcircuit board 12 having a plurality of cores; in particular, theindividual cores of the flexible printed circuit board 12 are eachindividually surrounded by the insulation element 14. It is conceivablefor the insulation element 14 to be formed in a film-like manner and inone piece with the insulation film 15. On the sensor element 11, a toolreceptacle 11.1 is arranged next to the insulation film 15. In thiscase, the insulation film 15 can at least electrically insulate amounting tool, which can be arranged in the tool receptacle 11.1, withrespect to the sensor element 11.

FIG. 4a depicts a further embodiment of a battery system 100 accordingto the invention. Here, the battery system 100 has a sensor apparatus 10according to the invention in a further possible embodiment. Anelectronic unit 30 is arranged on a cover 110 of the battery system 100,wherein the flexible printed circuit board 12 is connected, inparticular signal-connected, by way of its second end, preferably bymeans of a plug, to the electronic unit 30. Here, the flexible printedcircuit board 12 is designed in a spiral-shaped and three-layeredmanner. In this case, the flexible printed circuit board 12, which ispreferably formed with a plurality of cores, has the connecting element12 in the form of a flexible printed circuit board, an insulationelement 14 and a spring element 13. The spring element 13, the flexibleprinted circuit board 12 and the insulation element 14 are preferablyformed in a force-fitting, material-bonded and/or form-fitting manner. Asensor element 11, which contacts the battery cell 20, is arranged at afirst end of the flexible printed circuit board 12, which is of spiralform in FIG. 4a , with the result that state variables of the batterycell 20 can be transmitted to the electronic unit 30. In this case, thespring element 13 extends over the entire length of the connectingelement 12, as a result of which said connecting element is of spiralform and makes a spring force possible so that the sensor element 11 canbe brought into contact with the battery cell 20 and tolerances can becompensated.

FIG. 4b shows a further possible embodiment of a battery system 100according to the invention comprising a further possible embodiment of asensor apparatus 10 according to the invention. The flexible printedcircuit board 12 can preferably be formed with a plurality of cores and,as shown in FIG. 4b , can be of s-shaped/helical form. The flexibleprinted circuit board 12 has at least one spring element 13, wherein thespring element 13 and the flexible printed circuit board 12 are formedin one piece. The spring element 13 and the flexible printed circuitboard 12 are thus formed in a force-fitting, in particular amaterial-bonded and/or form-fitting manner. The helical spring element13 forms a spring force so that the flexible printed circuit board 12can press by way of a first end against the electronic unit 30 and byway of a second end against the battery cell 20. The flexible printedcircuit board 12 is preferably connected at its first end to theelectronic unit 30 by means of a plug.

FIG. 5 shows a further possible exemplary embodiment of a sensorapparatus 10 according to the invention in a battery system 100. In thiscase, the battery system 100 has a plurality of battery cells 20 (fourare shown). The sensor apparatus is arranged on a battery cell 20 sothat, in particular, the temperature of the battery cell 20 can bemonitored. In FIG. 5, the flexible printed circuit board 12 is of bentform and has a curved portion, which acts as a first spring element 13.Furthermore, a second spring element 13 is arranged on the flexibleprinted circuit board 12, wherein the second spring element 13 is offoamed and cube form. In this case, the spring element 13 of foamed formis arranged on the flexible printed circuit board 12 in such a way thatthe sensor element 11 is pressed at least against the battery cell 20.In FIG. 5, an insulation element 14 is arranged in the region of thesensor element 11, between the foamed spring element 13 and the flexibleprinted circuit board 12. As a result, the sensor element 11 is arrangedin a manner decoupled from the foamed spring element 13 and does nothave a common contact face. According to the invention, it isconceivable for the foamed spring element 13 to be adhesively bonded,welded and/or latched to the flexible printed circuit board 12. Theflexible printed circuit board 12 has a plug 16 at its one end 17, as aresult of which the flexible printed circuit board 12 and the electronicunit 30 are connected to one another.

The above explanation of the embodiments describes the inventionexclusively within the context of examples. It goes without saying thatindividual features of the embodiments can be combined freely with oneanother, insofar as technically appropriate, without departing from thescope of the present invention.

1. A sensor apparatus (10) for monitoring at least one battery cell (20)of a battery system (100), the sensor apparatus comprising a sensorelement (11) for detecting at least one state variable of the batterycell (20), at least one electrically and/or thermally conductiveconnecting element connected to the sensor element (11) so that thesensor element can be connected to the battery cell (20) and to anelectronic unit (30) of the battery system (100), wherein the connectingelement is formed as a flexible printed circuit board (12).
 2. Thesensor apparatus (10) according to claim 1, characterized in that theflexible printed circuit board (12) has at least one spring element(13).
 3. The sensor apparatus (10) according to claim 1, characterizedin that the spring element (13) and the flexible printed circuit board(12) are formed at least in a force-fitting, material-bonded and/orform-fitting manner.
 4. The sensor apparatus (10) according to claim 1,characterized in that the flexible printed circuit board (12) and/or thespring element (13) is of helical, spiral or z-shaped form.
 5. Thesensor apparatus (10) according to claim 1, characterized in that aninsulation element (14) is provided so that at least the flexibleprinted circuit board (12) is at least electrically isolated.
 6. Thesensor apparatus (10) according to claim 1, characterized in that aninsulation film (15) is arranged on the sensor element (11) so that thesensor element (11) is electrically and/or thermally insulated at leastin sections.
 7. The sensor apparatus (10) according to claim 1,characterized in that the spring element (13) at least partly comprisesfoam material.
 8. The sensor apparatus (10) according to claim 1,characterized in that the connecting element (12) has a plug (16) atleast at one end (17) of the connecting element.
 9. The sensor apparatus(10) according to claim 1, characterized in that the spring element (13)and/or the flexible printed circuit board (12) has at least one latchingconnection (18), clip connection or clamping connection, so that thespring element (13) and the flexible printed circuit board (12) can beconnected in a force-fitting manner.
 10. The sensor apparatus (10)according to claim 5, characterized in that the insulation element (14)comprises at least plastic and/or ceramic.
 11. The sensor apparatus (10)according to claim 6, characterized in that the insulation film (15)comprises at least plastic and/or ceramic.
 12. The sensor apparatus (10)according to claim 1, characterized in that the flexible printed circuitboard (12) has at least one spring element (13), wherein the springelement (13) and the flexible printed circuit board (12) are formed inone piece.
 13. The sensor apparatus (10) according to claim 1,characterized in that an insulation element (14) is provided so that atleast the flexible printed circuit board (12) is at least electricallyisolated with respect to the spring element (13).
 14. The sensorapparatus (10) according to claim 1, characterized in that theconnecting element (12) has a plug (16) at least at one end (17) of theconnecting element, wherein at least one tool receptacle (16.1) isarranged on the plug (16).
 15. A battery system (100) for storingelectrical energy and for supplying electrical energy to an electricmotor of a motor vehicle, the battery system comprising at least onebattery cell (20), an electronic unit (30) for monitoring the batterysystem (100) and at least one sensor apparatus (10) for monitoring atleast one battery cell (20), the sensor apparatus having a sensorelement (11) for detecting a state variable of the battery cell (20), atleast one electrically and/or thermally conductive connecting elementfor connection of the sensor element (11) to an electronic unit (30) ofthe battery system (100), wherein the connecting element is formed as aflexible printed circuit board (12).